This invention relates generally to pulse width modulation, and more specifically to converting a pulse code modulated data stream to a pulse width modulated signal.
A potentially useful operation in signal processing, such as digital signal processing of audio signals, is converting a digital pulse code modulated (PCM) data stream into a pulse width modulated (PWM) signal. The pulse code modulated data stream may be received from various sources, such as from a compact disk player or from a multi-media device. The resulting pulse width modulated signal may be applied to a switching amplifier to provide an amplified signal to a load, such as an audio speaker. A switching amplifier driven by a pulse width modulated signal has high efficiency and would therefore be desirable for many commercial applications. However, many conventional PCM to PWM converters introduce a high degree of harmonic distortion into the resulting output signal. One method that creates such distortion uses uniform sampling.
An alternative approach to uniform sampling that reduces distortion is referred to as natural sampling. Natural sampling refers to a theoretically ideal technique to convert PCM to PWM signals. One prior method has approximated natural sampling by performing iterative 3rd order polynomial curve fitting and root solving. While the above method is potentially quite useful, this method has not been widely used commercially since the computing operations to implement the method typically require a large amount of processing time.
Accordingly, there is a need for an improved method and apparatus for converting a digital PCM data stream into a PWM signal.